1. Field of the Invention
The present invention relates to a feeding apparatus for feeding a scrubbing solution to a scrubbing apparatus, for example, for scrubbing a semiconductor wafer and a replenishing method of a processing solution in the feeding apparatus.
2. Description of the Related Art
In processes of semiconductor device fabrication, the photolithography technology is used. In the photolithography technology, a resist is coated on a surface of a semiconductor wafer (hereinafter referred to only as "a wafer" ), and the coated resist is exposed to a predetermined pattern and developed. Thus, the predetermined pattern of resist film is formed on the wafer, and moreover the predetermined pattern of circuit is formed by film-formation and etching.
Hitherto, such a series of resist processing is performed using a coating and developing system in which, for example, a resist solution coating unit, a developing unit, a heating unit, a scrubbing unit, and the like are integrated.
In the scrubbing unit, liquid phase scrubbing by the use of a scrubbing solution in which, for example, NH4OH and H2O2 (both called processing solutions) are mixed is performed. These processing solutions deteriorate as time passes. Therefore, in a feeding apparatus for feeding a processing solution to the scrubbing unit, when a processing solution is stored in a storage container for more than a predetermined period of time without being used, the processing solution is drained from the container and the container is replenished with a new processing solution.
However, when the drainage of a processing solution from the container and the replenishment of the container with a processing solution are automatically performed in the feeding apparatus, it is possible that the supply of the processing solution is started after a predetermined time lapse from when the drainage of the processing solution is started by the use of a timer.
However, in the case where drainage of a processing solution from a container and replenishment of the container with a processing solution are automatically performed, there is a disadvantage that when a pipe for sending the processing solution from the container to a scrubbing unit is clogged, for example, there arises such a situation that an old processing solution remains in the container even if a set time of a timer expires and thereby the old processing solution and a new processing solution are mixed.